Experimental investigation on sol-gel transition of asphalt

This article is concerned about the sol-gel transition of asphalt by dynamic mechanical analysis. By sol-gel transition of asphalt, we mean here the transition from viscoelastic fluid to viscoelastic solid as the temperature is varied. In this investigation two types of asphalt of the same specification grade but manufactured by different process (blending and air blowing) were tested at unaged, short-term aged and long-term aged conditions. Sol-gel transition from G'-G cross-over, torque and normal force were captured. The transition point measured was frequency dependent when determined using G'-G crossover and torque and this frequency dependency vanished above 40 Hz. The measurement of normal force during these experimental investigation revealed interesting details. As the normal force recorded was only due to the contraction of the material during temperature sweep, the transition point measured was frequency independent. It was also found that the transition point calculated with normal force was close to the transition point calculated with G'-G cross-over and torque at higher frequencies. Also, the transition temperature increased as the material aged.